Expandable coil endoluminal prosthesis

ABSTRACT

A coiled stent ( 196 ) has a coiled stent body with a main body portion ( 106 ) and end portions ( 108 ). The end portions may be substantially less stiff than the body portion to help prevent tissue trauma. A graft material ( 124 ) may be used to cover at least the main body portion to create a coiled stent graft ( 122 ) in which adjacent turns ( 128 ) have gaps defined therebetween to create a generally helical gap ( 130 ). The coiled stent may have side elements ( 10 ) separated by connector elements ( 112 ) and be placeable in a contracted, reduced diameter state and in a relaxed, expanded diameter state. The connector elements are preferably generally parallel to the stent axis when placed in the contracted, reduced-diameter state, typically tightly wrapped around a placement catheter ( 136 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This is a continuation of U.S. patent application Ser. No.09/834,145 filed 12 Apr. 2001, now U.S. Pat. No. 6,660,032, which is acontinuation of U.S. patent application Ser. No. 09/400,955 filed 22Sep. 1999, now U.S. Pat. No. 6,645,237, which is a continuation-in-partof U.S. patent application Ser. No. 09/258,542 filed 26 Feb. 1999, nowU.S. Pat. No. 6,248,122. This is related to U.S. patent application Ser.No. 09/400,952 entitled Catheter With Controlled Release EndoluminalProsthesis and Method For Placing, filed 22 Sep. 1999, now U.S. Pat. No.6,238,430.

BACKGROUND OF THE INVENTION

[0002] The present invention provides devices and methods for theendoluminal placement of prostheses, particularly within the vascularsystem for the treatment of cardiovascular disease, such as vascularstenoses, dissections, aneurysms, and the like. The apparatus andmethods, however, are also useful for placement in other body lumens,such as the ureter, urethra, biliary tract, gastrointestinal tract andthe like, for the treatment of other conditions which may benefit fromthe introduction of a reinforcing or protective structure within thebody lumen. The prostheses will be placed endoluminally. As used herein,“endoluminally” will mean placement by percutaneous or cutdownprocedures, wherein the prosthesis is transluminally advanced throughthe body lumen from a remote location to a target site in the lumen. Invascular procedures, the prostheses will typically be introduced“endovascularly” using a catheter over a guidewire under fluoroscopicguidance. The catheters and guidewires may be introduced throughconventional access sites to the vascular system, such as through thefemoral artery, or brachial and subclavian arteries, for access to thetarget site.

[0003] An endoluminal prosthesis typically comprises at least oneradially expansible, usually cylindrical, body segment. By “radiallyexpansible,” it is meant that the body segment can be converted from asmall diameter configuration (used for endoluminal placement) to aradially expanded, usually cylindrical, configuration which is achievedwhen the prosthesis is implanted at the desired target site. Theprosthesis may be non-resilient, e.g., malleable, thus requiring theapplication of an internal force to expand it at the target site.Typically, the expansive force can be provided by a balloon catheter,such as an angioplasty balloon for vascular procedures. Alternatively,the prosthesis can be self-expanding. Such self-expanding structures areprovided by a temperature-sensitive superelastic material, such asNitinol, which naturally assumes a radially expanded condition once anappropriate temperature has been reached. The appropriate temperaturecan be, for example, a temperature slightly below normal bodytemperature; if the appropriate temperature is above normal bodytemperature, some method of heating the structure must be used. Anothertype of self-expanding structure uses resilient material, such as astainless steel or superelastic alloy, and forming the body segment sothat it possesses its desired, radially-expanded diameter when it isunconstrained, e.g., released from radially constraining forces asheath. To remain anchored in the body lumen, the prosthesis will remainpartially constrained by the lumen. The self-expanding prosthesis can bedelivered in its radially constrained configuration, e.g. by placing theprosthesis within a delivery sheath or tube and retracting the sheath atthe target site. Such general aspects of construction and deliverymodalities are well-known in the art and do not comprise part of thepresent invention.

[0004] The dimensions of a typical endoluminal prosthesis will depend onits intended use. Typically, the prosthesis will have a length in therange from 0.5 cm to 10 cm, usually being from about 0.8 cm to 5 cm, forvascular applications. The small (radially collapsed) diameter ofcylindrical prostheses will usually be in the range from about 1 mm to10 mm, more usually being in the range from 1.5 mm to 6 mm for vascularapplications. The expanded diameter will usually be in the range fromabout 2 mm to 42 mm, preferably being in the range from about 3 mm to 15mm for vascular applications.

[0005] One type of endoluminal prosthesis includes both a stentcomponent and a graft component. These endoluminal prostheses are oftencalled stent grafts. A stent graft is typically introduced using acatheter with both the stent and graft in contracted, reduced-diameterstates. Once at the target site, the stent and graft are expanded. Afterexpansion, the catheter is withdrawn from the vessel leaving the stentgraft at the target site.

[0006] Grafts are used within the body for various reasons, such as torepair damaged or diseased portions of blood vessels such as may becaused by injury, disease, or an aneurysm. It has been found effectiveto introduce pores into the walls of the graft to provide ingrowth oftissue onto the walls of the graft. With larger diameter grafts, wovengraft material is often used. In small diameter vessels, porousfluoropolymers, such as PTFE, have been found useful.

[0007] Coil-type stents can be wound about the catheter shaft in torquedcompression for deployment. The coil-type stent can be maintained inthis torqued compression condition by securing the ends of the coil-typestent in position on a catheter shaft. The ends are released by, forexample, pulling on wires once at the target site. See, for example,U.S. Pat. Nos. 5,372,600 and 5,476,505. Alternatively, the endoluminalprosthesis can be maintained in its reduced-diameter condition by asleeve; the sleeve can be selectively retracted to release theprosthesis. A third approach is the most common. A balloon is used toexpand the prosthesis at the target site. The stent is typicallyextended past its elastic limit so that it remains in its expanded stateafter the balloon is deflated. One balloon expandable stent is thePALMAZ-SHATZ stent available from the CORDIS Division of Johnson &Johnson. Stents are also available from Arterial Vascular Engineering ofSanta Rosa, Calif. and Guidant Corporation of Indianapolis, Ind.

SUMMARY OF THE INVENTION

[0008] The present invention is directed to an endoluminal prosthesisconfigured to help avoid trauma to a patient's tissue.

[0009] One aspect of the invention is directed to a coiled stent havinga coiled stent body with a main body portion and end portions. The endportions are substantially less stiff than the body portion to helpprevent tissue trauma.

[0010] The main body portion may include a ladder-like stent having edgeelements separated by connector elements. The end portions may haveinwardly-tapering portions with blunt tips. The inwardly-taperingportions may have lengths greater than the widths. The main body portionmay also be designed to have longitudinal sections with different radialstiffnesses.

[0011] A graft material may be used to cover at least the main bodyportion to create a coiled stent graft in which adjacent turns have gapsdefined therebetween to create a generally helical gap. The generallyhelical gap helps to promote a helical pattern of tissue ingrowth sothat even if substantial tissue ingrowth occurs, the vessel will be muchless likely to be sealed off than if the exposed tissue defined acircular pattern. The use of the generally helical gap may help speed uphealing because the generally helical gap may help cells to proliferatemore evenly between the coils and may enhance non-turbulent flow to helpreduce restenosis.

[0012] Further aspects of the invention relates to an endoluminalprosthesis having a body with side elements separated by connectorelements and a placement method therefore. The body is placeable in acontracted, reduced diameter state and a relaxed, expanded state. Theconnector elements are generally parallel to the axis of the body whenplaced in the contracted, reduced-diameter state, typically surroundinga placement catheter.

[0013] According to another aspect of the invention the endoluminalprosthesis includes a coiled body having first and second ends and amain portion therebetween. The main portion has an averagecross-sectional dimension of x. At least one of the first and secondends has a maximum cross-sectional dimension of about 5×to 25× and ablunt tip to avoid trauma to the patient's tissue. The tip typically hasa flattened, generally oval shape while the main body portion typicallyhas a rectangular cross-sectional shape.

[0014] Other features and advantages of the invention will appear fromthe following description in which the preferred embodiments have beenset forth in detail in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is an overall view of a catheter assembly using a straightstent embodiment;

[0016]FIG. 1A is an enlarged cross-sectional view taken along line 1A-1Aof FIG. 1;

[0017]FIG. 1B is an enlarged simplified partial cross-sectional view ofthe distal portion of the catheter of FIG. 1, with the addition of ageneral tubular external graft, to illustrate the relative relationshipbetween the various components;

[0018]FIG. 2A illustrates the catheter of FIG. 1A introduced into ablood vessel at a target site after the sheath has been pulled back toexpose the stent and balloon at the target site, the graft of FIG. 1Bbeing omitted from FIGS. 2A-2G for clarity of illustration;

[0019]FIG. 2B is similar to FIG. 2A with the distal portion of theballoon partially inflated to cause the first, distal stent portion todisengage from the first stent portion holder;

[0020]FIG. 2C is similar to FIG. 2B but after the balloon has beendeflated which permits the distal portion of the stent to spinrelatively freely and thus expand to press against the inside wall ofthe blood vessel;

[0021]FIG. 2D illustrates the balloon fully reinflated and showing thesecond, proximal end of the stent disengaged from the second stent endholder;

[0022]FIG. 2E is similar to FIG. 2D but with the balloon fully deflated;

[0023]FIG. 2F shows the stent in its second, expanded-diameter stateafter withdrawal of the distal portion of the catheter shaft;

[0024]FIG. 3A is an enlarged view illustrating a push wire extendingalong the catheter shaft, passing through a push wire tube to permit thesecond, proximal end of the stent to be disengaged from the cathetershaft;

[0025]FIG. 3B illustrates the first stent end holder and the first,distal end of the stent which slidably engages an opening formed in thefirst stent end holder;

[0026]FIG. 4A illustrates the stent of FIG. 2G with the external graftof FIG. 1B surrounding the stent and held against the inner wall of theblood vessel by the stent;

[0027]FIG. 4B illustrates the stent of FIG. 2G with an internal graft;

[0028]FIG. 4C illustrates fastening an internal graft to an externalstent using strips of graft material creating pathways for the stent;

[0029]FIG. 4D illustrates an alternative coil-type stent in which thestent comprises a pair of spaced-apart coiled stent wires;

[0030]FIG. 4E illustrates a stent graft in which parallel stent wiresare kept in a spaced-apart relationship by spacers, the coiled stentwires being covered on both the inside and the outside by graftmaterial, only a portion of the stent of FIG. 4A shown covered by thegraft material to illustrate the arrangement of the coiled stent wiresand spacers;

[0031]FIG. 5 shows a bifurcated version of the catheter and balloonallowing for deployment of a bifurcated prosthesis, the prosthesis notshown;

[0032]FIG. 6 illustrates a bifurcated stent;

[0033]FIG. 7 shows the bifurcated stent of FIG. 6 loaded onto thebifurcated catheter of FIG. 5 with the balloon deflated;

[0034]FIG. 7A is an enlarged cross sectional view taken along line 7A-7Aof FIG. 7;

[0035]FIG. 8 shows the bifurcated stent of FIG. 7 deployed in abifurcated vessel with the balloon inflated;

[0036]FIG. 9 shows the stent of FIG. 8 deployed in the vessel and thewithdrawal of the catheter;

[0037]FIG. 10 shows a bifurcated catheter with a spring member used tokeep the catheter shaft arms apart;

[0038]FIG. 11 illustrates a stent blank used to create a coiled stentsimilar to that shown in FIG. 4E;

[0039]FIG. 12 illustrates a stent blank similar to that of FIG. 11 buthaving different thickness along its length;

[0040]FIG. 13 illustrates a stent graft in a radially expandedcondition, the stent graft including a stent similar to that shown inFIG. 11 covered with a sleeve of porous graft material, the stent grafthaving a central turn with a greatly increased pitch for placement at abranching intersection;

[0041]FIG. 14 illustrates a stent graft similar to that of FIG. 13 butin which one end of the stent graft has much greater radially expandeddiameter than the other portion to accommodate a vessel having differentinternal diameters;

[0042]FIG. 15 illustrates an alternative embodiment to the stent graftof FIG. 13 in which the stent graft has a large expanded diameter andalso has the one turn with the greater pitch at one end of the stentgraft;

[0043]FIG. 15A shows a stent graft similar to that of FIG. 13 but withgenerally evenly-spaced turns;

[0044]FIG. 16A is an overall view of the distal end of a three-shaftdeployment catheter used to deploy the stent grafts of FIGS. 13-15;

[0045]FIG. 16B is an end view of the shafts of 16A;

[0046]FIG. 16C is an embodiment similar to the catheter of FIG. 16A butincluding only inner and outer shafts;

[0047]FIG. 16D illustrates a proximal end adapter mounted to theproximal end of the catheter of FIG. 16C;

[0048]FIG. 16E illustrates an alternative embodiment of the catheter ofFIG. 16C;

[0049]FIGS. 16F and 16G are simplified side and cross-sectional views ofa further alternative embodiment of the catheter of FIGS. 16A and 16B;

[0050]FIG. 17A illustrates the stent graft of FIG. 13 tightly wrappedabout the distal end of the catheter of FIGS. 16A and 16B and placedwithin a vessel with the intermediate portion of the stent graft at theintersection of the main and branching vessels;

[0051]FIG. 17B illustrates the release of the proximal half of the stentgraft;

[0052]FIG. 17C illustrates the release of the distal half of the stentgraft prior to the removal of the catheter shafts;

[0053]FIGS. 18 and 19 illustrate the placement of radiopaque marks atdifferent positions along a coiled ladder-type stent having a centralturn with a greatly increased pitch;

[0054]FIG. 20 illustrates one example of a radiopaque marker shaped topermit the determination of the orientation of the prosthesis as well asits location; and

[0055]FIG. 21 illustrates a coiled prosthesis having enlarged blunt endsto help prevent tissue trauma.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

[0056]FIG. 1 illustrates a catheter assembly 2 including broadly acatheter 4 extending from a proximal end adaptor 6, the catheter havingan introducer sheath 8 slidably mounted over the catheter. Proximal endadaptor 6 includes a body 10 to which a push wire manipulator 14 isslidably mounted. Proximal end adaptor 6 also includes an inflation port16, to permit a balloon, discussed below, to be inflated and deflatedduring use, and a guidewire port 17.

[0057] Catheter 4 includes elongate catheter shaft 18 defining threelumens therein. FIG. 1A illustrates an inflation lumen 20, coupled toinflation port 16, a guidewire lumen 22 housing a guidewire 24, theproximal end of the guidewire passing through guidewire port 17. Thecatheter shaft 18 also includes a push wire lumen 26 housing a push wiretube 28, a push wire 30 being housed within push wire tube 28. Push wire30 is connected to push wire manipulator 14 and is pushed and pulledthrough push wire tube 28 by the movement of manipulator 14. Push wiretube 28 is used to help prevent push wire 30 from buckling, which mayoccur during use due to the relatively thin diameter of the push wire,typically about 0.10 to 76 mm (0.004 to 0.030 inch). The distal end ofguidewire 24, not shown, is positioned near the tip 32 of catheter shaft18 and is used to help guide tip 32 through the body, typically throughblood vessels, as is conventional. During the typically percutaneousintroduction of the distal portion 34 of catheter 4 into thevasculature, sheath 8 is in the distal position shown in FIG. 1 to coverup the balloon 36, stent 38, and graft 40 as shown in FIG. 1B.

[0058] Once in position at the target site 42 in blood vessel 44, seeFIG. 2A, handle 46 of introducer sheath 8 is pulled in a proximaldirection to expose graft 40, stent 38, and balloon 36. Note that inFIGS. 2A-2F, graft 40 is not shown for clarity of illustration.

[0059] Stent 38 is a coil-type of stent typically made of 0.10 to 0.76mm (0.004 to 0.030 inch) diameter Nitinol wire. Stent 38 may be made ofother materials including stainless steel, Elgiloy®, acobalt-chromium-nickel alloy made by Elgiloy Inc., and polymers. Stent38, when in a relaxed state, typically has a diameter of about 2 to 30mm to accommodate blood vessel 44 having an internal diameter of about 2to 30 mm. The wire diameter, coil diameter, and other properties ofstent 38 may vary according to the particular body region to be accessedand the procedure to be conducted. In FIGS. 1B and 2A, balloon 36 is ina deflated condition while stent 38 is in a first, reduced-diameterstate with the coil-type stent 38 in torqued compression onto cathetershaft 18 and balloon 36. Stent 38 includes a proximal end 48, shown alsoin FIG. 3A, which is housed within a hollow interior of a stent endholder 50. Proximal end 48 of stent 38 can be selectively dislodged fromproximal stent end holder 50 by the distal movement of push wire 30through push wire tube 28. In this embodiment, proximal stent end holder50 is an extension of push wire tube 28 as suggested in FIG. 3A. Insteadof push wire 30, push wire tube 28 could be pulled into catheter shaft18 to release proximal end 48 of stent 38.

[0060] It may be desired that the length of stent 34 be about the samewhen in the reduced-diameter state as when in the relaxed,enlarged-diameter state. This is desirable to minimize shifting of thestent at the target site during deployment. The use of a coil-type stenthelps to achieve this by permitting the appropriate spacing the turns ofthe stent onto the balloon-covered catheter shaft when in areduced-diameter state. For example, stent 38 having a relaxed diameterof 6 mm, a relaxed length of 5 cm and 10 turns in a relaxed state, canbe wound onto the balloon-covered catheter shaft to assume areduced-diameter state with about 30 turns, a diameter of about 2.5 mmand the same length of about 5 cm. The results will vary depending onvarious factors, such as the pitch of the coil.

[0061] A proximal end 52 of balloon 36 is spaced-apart from stent endholder 50 by a distance sufficient to permit at least one turn, andpreferably one-and-a-half to two turns, of stent 38 to be wrappeddirectly around catheter shaft 18 without any of balloon 38 beingbetween stent 38 and catheter shaft 18. The purpose of this is toinhibit the dislodgment of proximal end 48 from stent end holder 50 uponthe initial inflation of balloon 36 as will be discussed in more detailbelow. Thus, the initial turn or turns of stent 38 are in effectivecontact with catheter shaft 18 because there is no portion of balloon 36between the turn or turns of the stent and the catheter shaft.

[0062] The distal end 54 of balloon 36 is positioned near the distalstent end holder 56. Accordingly, when the distal stent end 58 isengaged within distal stent end holder 56, stent 38 quickly startswrapping around balloon 36. Thus, upon inflation of balloon 36, distalstent end 58 is pulled from distal end holder 56 as shown in FIG. 2B.Note that in FIG. 2B, balloon 36 is only partly inflated. Inflation ofdistal end 54 of balloon 36 is aided in this embodiment by somewhat moreloosely wrapping stent 38 around the balloon at distal end 54 than overthe remainder of the balloon. This reduces the resistance to inflationof the balloon at distal end 54 thus permitting the expansion of thedistal end of stent 38 before expansion at its proximal end. Other waysto promote this initial expansion of distal end 54 of balloon 36, suchas making distal end 54 easier to expand than the remainder of theballoon or only partially retracting sleeve 8 or using a balloon withseparately inflatable proximal and distal portions, can be used.

[0063] After this partial expansion of balloon 36, the balloon isdeflated as shown in FIG. 2C. This permits stent 38 to more freelyexpand within blood vessel 44 so that a greater portion of the stent isin its expanded state in FIG. 2C than in FIG. 2B. FIG. 2D illustratesballoon 36 after having been fully inflated and the dislodgment ofproximal end 48 of stent 38 from proximal end stent holder 50 by movingpush wire 30 distally through the manipulation of push wire manipulator14. This dislodgment of proximal end 48 preferably occurs after the fullinflation of balloon 36; it could also occur before the full inflationof the balloon as well.

[0064]FIG. 2E illustrates balloon 36 deflated leaving stent 38 in itsexpanded-diameter state pressing graft 40, not shown in FIGS. 2A-2F butshown in FIG. 4A, against the inner wall of blood vessel 44. Though notalways necessary, it may be desired to move sheath 40 in a distaldirection to cover balloon 36 prior to removing the distal portion ofthe catheter shaft. FIG. 2F illustrates stent 38 in itsexpanded-diameter state after removal of catheter shaft 18 and sheath 8.It can be noted that in FIGS. 1B and 4A the length of graft 40 isshorter than the length of stent 38; this helps to ensure that the endsof graft 40 are pressed against the interior of blood vessel 44.

[0065] In use, the user introduces distal portion 34 of catheter 4 into,for example, a suitable blood vessel 44 and directs tip 32 of cathetershaft 18 to a target site 42 using guidewire manipulator 12 andappropriate visualization techniques as is conventional. Balloon 36 ispartially inflated through inflation port 16 to the condition of FIG. 2Bcausing distal stent end 58 to be dislodged from distal stent end holder56. Balloon 36 is then deflated to permit a distal portion of stent 38to more fully expand within blood vessel 44. Balloon 36 is then fullyexpanded as shown in FIG. 2D and push wire 30 is extended by moving pushwire manipulator 14 in a distal direction causing proximal end 48 ofstent 36 to be dislodged from proximal stent end holder 50;alternatively, push wire 30 could be extended to first dislodge proximalend 48 of stent 38B from proximal end stent holder 50 and then balloon36 could be fully expanded. The inflation of balloon 36 also expandsgraft 40. Balloon 36 is then deflated as shown in FIG. 2E and withdrawninto sheath 8. A distal portion of catheter shaft 18 and balloon 36therewith are then withdrawn from target site 42 in blood vessel 44 (seeFIG. 2F) leaving stent 38 and graft 40, which together constitute astent graft 59, in place as shown in FIG. 4A.

[0066]FIG. 4B illustrates an alternative embodiment in which graft 40Ais an internal graft coupled to stent 38. One method of couplinginternal graft 40A to stent 38 is through the use of one or more strips60 of graft material. Pockets, not shown, are created between stent 40Aand strips 60 to permit stent 38 to pass between the two. The gaps arerelatively large to prevent graft 40A from being overly deformed duringthe deployment of the stent and graft.

[0067]FIG. 4D illustrates a stent 38A made up of a pair of spaced-apartcoiled stent wires joined together at their ends. To permit the ends ofstent 38 to be secured to catheter shaft 18, the stent end holderscould, for example, be modified to accommodate the generally U-shapedends or the ends could be squeezed together or otherwise made to form apointed end as suggested by the dashed lines at one end of stent end38A.

[0068]FIG. 4E illustrates a presently preferred embodiment in which astent 38B is made up of a pair of coiled stent wires 62 joined togetherand maintained in a spaced-apart relationship by spacer wires 64 tocreate a ladder-like stent 38B. A strip 66 of graft material is securedto coiled stent wire 62 to form a spiral graft 40B surrounding stent 38Bto lie on both the inside and the outside of the stent. Only a portionof stent 38B is covered with strip 66 to illustrate the construction ofthe stent. Strip 66 of graft material can be adhered to stent 38B in avariety of ways including use of an adhesive, heat welding, or makingstrip 66 in the form of a tube or a double-sided strip with a hollowinterior which encases coiled stent wires 62. It can be seen that onlyone of the two coiled stent wires 62 extend outwardly at each end ofstent 38B to form the proximal end 48B and the distal end 58B of stent38B.

[0069] Ladder-like stent 38B could also be made from a tube or sheet ofstent material by, for example, stamping, laser cutting, waterjetcutting or other suitable processes. It is expected that processes whichdo not overly heat the stent material, such as waterjet cutting, may bepreferred. The graft material can be in the form of a tube of graftmaterial which is slid over ladder-like stent 38B and secured in placeby, for example, suturing the ends of the graft material.

[0070]FIG. 5 shows a distal portion 34D of a bifurcated catheter madeaccording to the invention with like reference numerals referring tolike elements. Catheter shaft 18D includes first and second arms 70, 72terminating at first and second tips 74, 76. In FIG. 5 neither a stent,shown in FIG. 6, nor graft material is illustrated for clarity ofillustration. Balloon 36D is a bifurcated balloon having a first portion78 extending along first arm 70 and a second portion 80 extending alongsecond arm 72. Proximal stent end holder 50 is carried on catheter shaft50D while distal stent end holder 56D is positioned along first arm 70D.The stent end holders 50D, 56D are similar to stent end holders 50, 56illustrated in FIGS. 3A and 3B with the hollow tubular members extendingdistally for proximal stent end holder 50 and proximally for distalstent end holder 56D. A second distal stent end holder 82 is carriedalong second arm 72 and has a distally extending open-ended tube 84corresponding to push wire tube 28D in that it also extends in a distaldirection and uses a push wire to disengage the end of a stent fromwithin the push wire tube 84. As discussed above, other methods forremoving the ends of the stents from push wire tubes 28D, 84 such asretracting the push wire tubes proximally, could also be used.

[0071]FIG. 6 illustrates a bifurcated stent 38D having a main portion 86and first and second arms 88, 90 which are wrapped around main portionof catheter shaft 18D and first and second arms 70, 72 respectively. Arm88 is an extension of main portion 86; arm 90 is joined to arm 88 andmain portion 86 at junction 102. Proximal end 48D of stent 38Dcorresponds to proximal end 48 of stent 38 as shown in FIG. 3A whiledistal end 58D of stent 38D corresponds to distal stent end 58 of stent38 shown in FIG. 3D. Proximal and distal ends 48D, 58D engage proximaland distal stent end holders 50D, 56D in manner similar to those ofFIGS. 3A and 3B. However, the distal end 92 of second arm 90 may have areverse bend.

[0072] As shown in FIG. 7A, catheter shaft 18D defines three lumens,inflation lumen 20D, guidewire lumen 22D, housing tube guidewires 24D,one for each arm 70, 72, and a push wire lumen 26D housing push wiretubes 28, 84 with push wires 30D slidingly passing within the push wiretubes 28D, 84.

[0073]FIG. 7 illustrates distal catheter portion 34D with balloon 36D ina collapsed state, stent 38D wrapped around both balloon 36D and distalportion 34D, and showing the outline of a branched vessel 44D shown indashed lines. Again, as with FIGS. 2A-2F, graft material is not shownfor ease of illustration. However, as with the embodiments of FIGS. 1-4,graft material is typically used with stent 38D. Of course other typesof stents, other than the coiled bifurcated stent shown in FIG. 6, couldbe used as well. The placement of stent 38D occurs in substantially thesame fashion as can occur with the straight stent described above. Themain difference is that proximal ends 48D and 92 of stent 38D are bothreleased using push wires 30D while distal stent end 58D is released bythe partial inflation of balloon 36D. FIG. 8 illustrates the result ofhaving gone through the stent end release cycle, that is typicallypartial inflation, which releases stent end 58D, deflation and then thefull inflation and release of stent ends 48D, 92. After stent 38D hasbeen expanded, distal catheter portion 34D and balloon 36D therewith areremoved from the bifurcated target site as suggested in FIG. 9. Again,graft material is not shown for clarity of illustration. As with theabove embodiments, graft material may not be, but often is, used withthe stent or other prosthesis.

[0074]FIG. 10 illustrates a distal catheter portion 34E similar to thatshown in FIG. 5 in which the first and second arms 70, 72 are biasedoutwardly at their junction 94 by a biasing element 96 which tends toseparate arms 70, 72 from one another. Biasing element may be made of avariety of materials, such as a leaf spring or, as illustrated, atriangular section of a resilient spongy material such as silicone orpolyurethane. Using biasing element 96 helps to ensure arms 70, 72 aredirected down different vascular segments 98, 100. To do so distalcatheter portion 34E is typically housed within sheath 8 until justabove the target site. At that point, distal portion 34E is extended outthrough the open distal end of introducer sheath 8 permitting arms 70,72 to move freely into vascular segments 98, 100. This movement may beaided using guidewires 24D in addition to biasing element 96.

[0075] Modifications and variation may be to the above-describedcatheter assembly and method may be made. For example, it may not benecessary to only partly inflate the balloon as indicated in FIG. 2B;rather, it may be desired to fully inflate the balloon to release distalstent end 58 from distal stent end holder 56. Also, it may not benecessary to deflate the balloon after the full or partial inflation ofthe balloon as shown in FIG. 2C. In a preferred embodiment, a coiledstent is placed in torqued compression onto the catheter shaft andballoon. Other types of radially expanding stents, which may or may notbe self-expanding, can be used as well. For example, tubes of stentmaterial having numerous axially extending slits which permit the tubeto be expanded radially in a diamond-like pattern using the balloon canbe used. The stent could also be made of a temperature-sensitiveshape-memory material. In the preferred embodiment, balloon 36 isnecessary to expand graft 40 from its reduced-diameter state of FIG. 1Bto its expanded-diameter state of FIG. 4A; graft material may be usedwhich does not require a balloon to place it into its fully expandedcondition. In the preferred embodiment, graft 40 is an expandable,porous PTFE graft material such as that available from IMPRA, Baxter, W.L. Gore or Atrium. Other types of graft material, such as polyester orpolyurethane, can be used. Instead of mechanically releasing proximalend 48 of stent 38, the proximal end can be held and selectivelyreleased by electrolytic methods as shown in U.S. Pat. No. 5,122,136 toGuglielmi, et al. Distal stent end 58 could be releasably coupled tocatheter shaft 18 for release by inflation of balloon 36 by other thanholder 56, such as through a releasable or breakable tether, a clip orother fastener, adhesive or other releasable or breakable structure. Theholding and selective release of proximal stent end 48 could be by usinga range of conventional or unconventional holders; for example, thedistal end of sheath 8 could be left to cover the proximal end 52 ofballoon 36 during the initial inflation of balloon and then pulled backto uncover the proximal balloon end for the subsequent inflation of theballoon. Pull or push wires could be used to actuate a catch to releaseproximal stent end 48. Conventional techniques, such as those shown inU.S. Pat. Nos. 5,372,600; 5,476,505; 5,683,451; 5,443,500; 4,913,141;5,246,445; 5,360,401; 5,201,757; 4,875,480; 4,848,343; 4,732,152; and4,665,918, and those shown in WO 97/07756 and WO 94/16629, may also beused to release proximal stent end 48.

[0076] Bifurcated embodiments have been shown illustrating use of asingle balloon. If desired, a number of separate balloons could be usedinstead of a single balloon. For example, three separate balloons couldbe used, one for each branch of the stent. The three balloons could beall coupled to a single inflation lumen; in such case the three separateballoons would act similarly to the single balloon. However, if eachballoon were separately inflatable, more than one of the stent endscould be released through the inflation of the various balloons. Stent38D is shown with main portion 86 and first and second arms 88, 90secured together at a common location 102. It may be desired to have,for example, second arm 90 be joined to a section of stent 38D betweenmain portion 86 and first arm 88 by a sliding connection; this may beuseful to help properly seat or orient the stent or a stent graft withinthe bifurcated vessel. First arm 88 is shown as a single continuous coilin FIG. 6. If desired, first arm 88 could include one or more separatesections of stent to create the first arm. Instead of having a singlecatheter split into two catheter arms, second arm 72 could actually be aseparate catheter extending through the interior of catheter shaft 18D;this would facilitate inflating a balloon associated with the second armseparately from the one or more other balloons associated with the mainportion of the catheter shaft and the first arm. It may also permit thesecond arm of the catheter shaft to move longitudinally relative to themain catheter shaft and the first arm of the catheter shaft.

[0077]FIG. 11 illustrates a stent blank 104 used to create a coiledstent similar to that shown in FIG. 4E. Stent blank 104 includes a mainbody portion 106 and first and second end portions 108. Main bodyportion 106 includes side edge or rail elements 110 connected byconnector or rung elements 112. Rung elements 112 are, as shown in FIG.11, at an angle to rail elements 110 so that when stent blank 104 isformed into a coiled stent and tightly wrapped about an introducercatheter, such as in FIG. 17A, rung elements 112 are axially-extendingso that they lie flat for a tighter wrap.

[0078] End portions 108 are thinner and thus more flexible than mainbody portion 106. In addition, end portions 108 have an inwardlytapering portion 114 terminating at a blunt tip 115. The shape of endportions 108 and the lessened stiffness of the end portions, compared tobody portion 106, help to prevent tissue trauma during use. This type ofcoiled stent in which the end portions 108 are less stiff than the mainbody portion 106 can find particular utility in stabilizing a traumaticinjury site within a patient, such as in the case of a dissection, flapor false lumen. End portion 108 could also be stiffer than main bodyportion; this embodiment may be useful, for example, when treatingocclusive disease on either side of a branch vessel.

[0079]FIG. 12 illustrates a stent blank 104A similar to stent blank 104of FIG. 11 but in which main body portion 106A has three differentradial stiffnesses. That is, main body portion 106A has a first, centrallongitudinal section 116 of a first, greater stiffness, and second andthird longitudinal sections 118, 120 on either side of first section116. Sections 118, 120 are successively thinner and thus havesuccessively lower radial stiffnesses when stent blank 104A is formedinto a coiled stent. End portion 108A acts as the fourth longitudinalsection with the least radial stiffness of any of the sections in thisembodiment. Instead of a set of generally discrete radial stiffnesses,the radial stiffness could vary continuously along at least part of thelength of stent blank 104A, and then along the resulting stent body.

[0080] In addition to providing less traumatic end portions 108, 108A, acoiled prosthesis formed from either of stent blanks 104, 104A, whenuncoiling, will have a tendency to open up first in the center, becauseof the greater stiffness at the center, followed by the ends. This helpsto reduce the degree to which the end portions 108, 108A are draggedalong the surface of the vessel or other hollow body structure as theprosthesis is released.

[0081]FIGS. 13, 14, 15 and 15A illustrate four stent graft embodiments122, 122A, 122B, 122C. Stent graft 122 includes a ladder-type coiledstent formed from stent blank 104 and covered with tubular graftmaterial 124. Graft material 124 is preferably porous PTFE or ePTFE. Theends 126 of graft material 124 are sealed, or for example, by using anadhesive or by placing a suitable heat seal material, such as FEP(fluorinated ethylene propylene) or other thermoplastic materials,between the layers of the graft material 124 and applying heat andpressure. The porous nature of the graft material permits sealing inthis manner in spite of the inert nature of PTFE. In addition, a directbond of the PTFE to itself, via a process known as sintering, may beemployed. Other methods for sealing ends 126 could also be used. Coiledstent graft 122 includes a number of spaced apart turns 128 defining agenerally helical gap 130 therebetween. The helical nature of the gap130 is believed to help prevent restenosis in two ways. First, thehelical nature of stent graft 122 and of gap 130 is expected to helpinduce a blood flow pattern which helps to reduce plaque build up.Second, if plaque build up does occur along the edges of helical gap 13,the helical nature of gap 13 is expected to help cells to proliferatemore evenly between adjacent turns 128 and may enhance non-turbulentflow to help reduce restenosis.

[0082] The average width of helical gap 130 is equal to about 0% to1200% of the average width of turns 128. More typically the averagewidth of gap of 130 is about 50% to 800% of the average width of turns128 when stent graft 122 is deployed. Also, stent graft 122 has agenerally constant pitch except at its central region. The pitch of acentral turn 132 of stent graft 122 is substantially greater than thepitch of its adjacent turns 128 to accommodate placement of stent graft122 at the intersection of a main or first vessel and a branching vesselas will be discussed in more detail with reference to FIGS. 17A-17C.

[0083]FIG. 14 illustrates a stent graft 122A in which a central turn132A also has an increased pitch as opposed to adjacent turns 128A.However, the turns on one side of central turn 132A have a largerfully-expanded diameter than turns on the other side to accommodatetransition between smaller and larger diameter vessels.

[0084]FIG. 15 illustrates a stent graft 122B designed for placement withthe end turn 134 having a substantially greater pitch than its adjacentturn 128B. Stent graft 122B is used when one end of the stent graft isto be positioned at the intersection and main and branching vessels sothat the stent graft extends to one side of the intersection as opposedto both sides as in the embodiments of FIGS. 13 and 14. FIG. 15Aillustrates stent graft 122C, which may be used at locations other thanbifurcations, having generally uniformly spaced turns 128C.

[0085] FIGS. 16A-16B illustrate a catheter 136 used for deploying thestent grafts of FIGS. 13 and 14. Catheter 136 includes outer,intermediate and inner rotating, telescoping shafts 138, 140, 142 eachhaving a distal end 144, 146, 148. Each of the shafts has a prosthesisportion holder 150, 150A, 150B at its distal end 144, 146, 148.Prosthesis portion holders 150, 150A, 150B include pull wires 152, 152A,152B which pass along axially-extending lumens 154, 154A, 154B formed inthe body of shafts 138, 140, 142, out of exit holes 156, 156A, 156B,across gaps 158, 158A, 158B and back into reinsertion openings 160,160A, 160B. Pull wires 152, 152A, 152B pass through and engage differentportions of, for example, stent graft 122 and secure those portions ofthe stent graft to shafts 138, 140, 142. As shown in FIG. 17A,prosthesis portion holder 150B at distal end 148 of inner shaft 142engages the distal end 166 of stent graft 122. Holders 150, 150A atdistal ends 144, 144A of outer and intermediate shafts 138, 140 engageproximal end 168 and central turn 132 of stent graft 122, respectively.One or more of shafts 138, 140, 142 may be braided to enhance torquingstiffness to aid rotation.

[0086]FIG. 16C illustrates the distal end of a catheter 136A includingonly two shafts, outer shaft 138A and inner shaft 142A. Catheter 136A istypically used when placing an endoluminal prosthesis of the type whichdoes not have a central turn with an increased pitch, such as those ofFIGS. 15 and 15A, and thus does not need a catheter with an intermediateshaft.

[0087]FIG. 16D illustrates, in a simplified form, a proximal end adapter170 mounted to the proximal end of catheter 136A of FIG. 16C. Proximalend adapter 170 includes distal and proximal portions 172, 176 throughwhich catheter 136A passes. Proximal end adapter 170 provides for therotation of either or both shafts 138A, 142A through the manipulation ofthumb wheel 174 mounted to portion 176. A flip lever 175 extends fromdistal portion 172 and is movable between secured and released positionsto either secure shafts 138A, 142A to one another or to permit shafts138A, 142A to move axially relative to one another. Pull wires 152, 152Bare normally secured to their respective shafts 138A, 142A by deploymentknobs 178, 180; pulling on deployment knobs 178, 180 releases pull wires152, 152B, respectively to permit the pull wires to be pulled to releasethe endoluminal prosthesis from the appropriate holder 150, 150B.

[0088]FIGS. 16F and 16G illustrate a further three-shaft embodiment ofthe invention similar to the three-shaft embodiment of FIGS. 16A and16B. Instead of using lumens 154 to house pull wires 152, tubularmembers 162, 162A, 162B, typically hypotubes, could be secured to theoutside of the shafts 138B, 140B, 142B. Gaps or breaks are provided atthe distal ends of hypotubes 162, 162A, 162B to define the gaps 158,158A, 158B.

[0089]FIG. 17A shows stent graft 122 of FIG. 13 tightly wrapped aboutcatheter 136. Distal end 166, proximal end 168 and central turn 132 ofstent graft 122 are secured to distal ends 148, 144 and 146 of inner,outer and intermediate shafts 142, 138 140 by prosthesis portionsholders 150. Stent graft 122 is housed within a main vessel 182 withcentral turn 132 aligned with the intersection 184 of main vessel 182and branching vessel 186. To help ensure proper placement of centralturn 132 at intersection 184, stent graft 122 has one or more remotevisualization markers at or adjacent to turn 132. Radiopaque markers188, 190 192 are shown in FIG. 18 at distal, intermediate and proximalportions of the central turn 194 of stent 196. Radiopaque markers may beshaped to provide information as to both location and orientation ofstent 196 on the catheter. For example, radiopaque marker 190A of FIG.19 has a broad central portion 190B extending between rail elements 110and arm portions 190C extending along rail elements 110; this permitsmarker 190A to provide both location and orientation information aboutstent 196A. Orientation marker 190A is configured so that the viewer candetermine whether the turn is facing the viewer or is away from theviewer based upon the marker's orientation. Various other marker shapesto provide both location and orientation can also be used.

[0090] Radiopaque markers may also be used on the placement catheteritself. For example, radiopaque markers 191, 193, 195 are used on shafts138B, 140B, 142B aligned with their respective holders 150, 150A, 150B,as shown in FIG. 16F, to indicate the location of the holders.Radiopaque marker 193 is shown to be configured as an orientationspecific marker to help in the proper placement of the prosthesis. FIG.20 illustrates the shape of an orientation-specific radiopaque marker197 which could be placed, for example, on shafts 138, 140, 142 at oneor more of the holders 150 of the embodiments of FIGS. 16A, 16C and 16E.Radiopaque or other remote visualization markers may also be used atother positions along the endoluminal prosthesis, such as at each end,or along the placement catheter.

[0091]FIG. 17B illustrates the release of proximal end 168 of stentgraft 122 while FIG. 17C illustrates the subsequent release of distalend 166 of stent graft 122. It should be noted that central turn 132remains secured to intermediate shaft 140 while the distal and proximalends 166, 168 of stent graft 122 are released to ensure that the openregion of central turn 122 remains facing intersection 184 to helpensure substantially unrestricted fluid flow between main vessel 182 andbranching vessel 186. It should also be noted that prior to releasingthe stent graft, the number of turns can be increased or decreased bythe relative rotation of shafts 138, 140 and 142. Also, the length ofstent graft 122 can be changed by the relative axial sliding motionamong outer, intermediate and inner shafts 138, 140, 142. For example,instead of simply releasing proximal end 168 of stent graft 122 to theposition shown in FIG. 17B, it may be desired to rotate outer shaftrelative to intermediate shaft 140, keeping intermediate and innershafts 140, 142 stationary so to unwind the proximal half of the stentgraft to ensure that the stent graft is properly positioned prior toreleasing the stent graft. Similarly, both outer shaft and inner shaftscan be rotated while maintaining intermediate shaft stationary to createthe expanded diameter condition of FIG. 17 prior to releasing anyportion of the stent graft. In this way the physician can ensure thatstent graft 122 is properly positioned, especially with respect tocentral turn 132. If necessary or desired, intermediate shaft 140 couldbe, for example, rotated relative to outer and inner shafts 138, 142 tohelp properly position or reposition central turn 132.

[0092]FIG. 17A also shows how by properly selecting the angle ofconnector elements 112 relative to side elements 110 for a placementcatheter of a particular outside diameter, connector elements 112,indicated by dashed lines in FIG. 17A, will lie generally parallel tothe axis of stent graft 122. This permits connector element 112 to liecloser to catheter 136, to provide a much smoother wrap when in itscontracted, reduced-diameter state, than would result if connectorelements were not generally parallel to the axis in such a state. Thisaxial orientation can be contrasted with the off-axis orientation ofconnectors 112 when in the expanded diameter state of FIG. 17C. Thesmoother outer surface of stent graft 122 enhances the ease of insertionof the stent graft within a hollow body organ, such as blood vessel 182.

[0093] As discussed above with reference to FIGS. 11 and 12, endportions 108, 108A of sent blanks 104, 104A are less stiff than mainbody portion 106, 106A, as well as having rounded, blunt tips 116, 116A.FIG. 21 illustrates a coiled prosthesis 198 in which the main body 200has an average cross-sectional dimension of x while the enlarged bluntends 202 have a maximum cross-sectional dimension 204 of 5x to 25x, andmore preferably 5x to 10x. In one example main body 200 has arectangular cross-sectional shape with a minimum width of 0.025 mm(0.001 in) and a maximum width of 1 mm (0.040 in); enlarged blunt endhas a thickness of 0.025 mm (0.001 in) and a maximum cross-sectionaldimension 204 of lcm (0.4 in). This configuration of the ends 202 ofprosthesis 198 helps reduce trauma to the patient's tissue by making theends of the prosthesis less stiff and also by providing a much greatersurface area so to reduce the pressure exerted against the tissue, asopposed to what could be exerted by a coiled prosthesis having aconstant cross-sectional dimension. The example of FIG. 21 could bemodified so that ends 202, rather being solid, are made from loops ofwire with open centers.

[0094] Modification and variation can be made to the above describedinventions without departing from the subject of the inventions asdefined in the following claims. For example, connectors 112 could beoriented perpendicular to rail elements 110, graft material 124 could beplaced upon only a portion of the underlying stent or on only one sideof the underlying stent. Placement catheter 136 could include fewer oradditional telescoping rotatable shafts. The telescoping shafts may notneed to be coaxial shafts slidable within or over one another; thetelescoping shafts could be, for example, solid and/or tubular elongatemembers positioned side-by-side. Holders 150 could be constructeddifferently; for example, if the sequence of releasing the prosthesis isknown it may be possible to use a single pull wire instead of threeseparate pull wires.

[0095] Any and all patents, applications, and printed publicationsreferred to above are incorporated by reference.

What is claimed is:
 1. A coiled endoluminal prosthesis comprising: abody comprising a coiled ribbon of material; the body comprising a mainbody portion and first and second end portions, the main body portioncomprising first and second edge elements separated by connectorelements, at least substantially all of the elements between the firstand second edge elements being said connector elements; the main bodyportion having a maximum width and the end portions having a maximumwidth no greater than the maximum width of the main body portion; saidbody movable between a reduced diameter state, extending along a bodyaxis, and an expanded diameter state; and all said connector elementsbeing at an acute angle to the edge elements when in the expandeddiameter state, said angle chosen so that all of said connector elementslie generally parallel to the body axis when in the reduced diameterstate so to provide a smoother appearance when in the reduced diameterstate.
 2. A coiled endoluminal prosthesis according to claim 1 whereinthe end portions are substantially less stiff than the main bodyportion.
 3. A coiled endoluminal prosthesis according to claim 1 whereinsaid end portions each have an inwardly-tapering portion with a blunttip.
 4. A coiled endoluminal prosthesis according to claim 1 wherein themain body portion comprises first, second and third longitudinalsections each having a different radial stiffness.
 5. A coiledendoluminal prosthesis according to claim 1 wherein the stiffness of themain body portion continuously varies along at least part of its length.6. The coiled endoluminal prosthesis according to claim 1 furthercomprising an orientation-specific marker carried by the body so to aidproper rotary orientation and longitudinal placement of the prosthesis.7. The coiled endoluminal prosthesis according to claim 1 wherein theend portions comprise generally U-shaped members, said generallyU-shaped members being thinner and more flexible than the edge andconnector elements of the main body portion.
 8. The coiled endoluminalprosthesis according to claim 1 wherein the end portions have alongitudinally-extending length and a laterally-extending width, saidlength being greater than said width.